The present invention relates to a video output apparatus and, more particularly to a video output apparatus that is capable of performing real-time processing for a main picture including moving picture and still picture information, a sub-picture including subtitle information, and OSD (On Screen Display) data including menu and title image information with improved controllability, when these data are output.
In recent years, with great advances in multimedia, there have been proposed various types of reproducing apparatus in the field of video in consideration of digital video broadcasting. In the future, it is thought that a larger volume of information should be sent from a broadcasting station. Then, it will be required for some reproducing apparatus to perform processing beyond its ability. When such processing beyond its specification is required, viewers might see degraded-quality video on the screen and might feel displeased with it. Conventionally, when a moving picture is displayed on a personal computer, it is possible to reproduce the same while diminishing the viewers"" feeling of strangeness and in accordance with specifications of the reproducing apparatus, with the number of frames to-be-displayed per unit of time being reduced, i.e., with a frame chute being applied. However, in high vision broadcasting, which should provide high-quality video image, such processing as a frame chute would inevitably give the viewer displeasure.
It is also possible that the reproduction processing capabilities are realized by the use of a control device that has capabilities satisfying the processing, on the basis of the worst value in processing cycles required for the video output process. However, such construction of the video output apparatus results in a complicated construction of a control device. Besides, since the control device operates at a high frequency, this provides problems to environments.
In the prior art video output apparatus, in a case where a load is placed on the apparatus that is beyond its processing ability even when a load beyond its processing ability is required for the apparatus, no effective methods for processing data in real time have been proposed, without giving viewers displeasure with reproduced video.
In view of progress of multimedia that requires enormous amount of information to be transmitted, there have been demands for a video output apparatus, which is capable of handling enormous amount of information.
It is an object of the present invention to provide a video output apparatus which is capable of outputting video in a real-time video output process without displeasing viewers with it, even if the load placed on the apparatus exceeds its processing abilities.
Other objects and advantages of the invention will become apparent from the detailed description that follows. The detailed description and specific embodiments described are provided only for illustration since various additions and modifications within the spirit and scope of the invention will be apparent to those skill in the art from the detailed description.
According to a first aspect of the present invention, a video output apparatus comprises: video data processing means for processing plural pieces of video data of different types and outputting the resulting video data to a monitor; video processing delay detecting means for detecting delay by deciding whether processing for the plural pieces of video data performed by the video data processing means is completed in real time, when it is output to the monitor; and video data processing control means for controlling the video data processing means so that the processing performed by the video data processing means, which is to be allocated for one line period, is reduced when the video processing delay detecting means detects delay. Therefore, the real-time processing is guaranteed. In addition, viewers might not feel displeased with displayed video. Besides, there is little increase in a program size, and a control device required for processing need not have a complicated construction and operate at high frequencies.
According to a second embodiment of the present invention, in the video output apparatus of the first aspect, the video data processing control means controls the video data processing means by setting priority of the video data processing when the processing is reduced. Therefore, video data processing to be reduced can be selected among alternatives.
According to a third embodiment of the present invention, in the video output apparatus of the second aspect, the priority is determined according to distance from a user""s view point to a display image on the monitor. Therefore, a user-oriented display can be realized.
According to a fourth aspect of the present invention, in the video output apparatus of the second aspect, the priority is determined according to display information set in the video data. Therefore, important information such as a program title is displayed with priority, and users will not miss it.
According to a fifth aspect of the present invention, in the video output apparatus of the first aspect, at least one of the processes for the plural pieces of video data to be performed during one line period is divided into plural processes. Therefore, capacities of buffer memories can be reduced.
According to a sixth aspect of the present invention, in the video output apparatus of the first aspect, the video processing delay detecting means detects delay in units each comprising either a predetermined number of fields or a predetermined number of frames. Therefore, a load placed on hardware caused by detecting delay can be reduced.
According to a seventh aspect of the present invention, in the video output apparatus of the first aspect, the video processing delay detecting means detects delay in units each comprising a predetermined number of lines. Therefore, a highly precise image can be displayed.
According to an eighth aspect of the present invention, in the video output apparatus of the first or fifth aspect, the video data processing control means skips at least one part of video data processing among the processing for the plural pieces of video data, to reduce the processing. Therefore, the quality of the displayed image is not degraded, and desired video data can be referred to.